Barrier compositions and articles made therefrom

ABSTRACT

Improved oxygen barrier and oxygen absorbing compositions and structures comprising blends of xylylene group-containing polyamides and cobalt octoate and xylylene group-containing polyamides, polyesters and cobalt octoate are disclosed and claimed. These blends have superior barrier properties and clarity obtained by controlling the degree of orientation and the amount of cobalt. These novel blends are used as single layers and as the core layer in multiple layer films, structures and articles. When used in multiple layer structures, the adjacent layers are comprised of polyesters and/or polyamides. The structures made from the blends of the present invention have a clarity that is superior to structures previously known in the art.

[0001] This application is a continuation-in-part of application Ser.No. 07/472,400, filed Jan. 31, 1990, entitled “Improved BarrierComposition and Articles Made Therefrom”, incorporated herein byreference. The present invention relates to further improvements in thecomposition and articles of application Ser. No. 07/472,400.

[0002] A continuation-in-part application, Ser. No. 07/761,490 entitled“Improved Barrier Composition and Articles Made Therefrom”, was filed onSep. 18, 1991 as a continuation of application Ser. No. 07/472,400.Application Ser. No. 07/761,490 is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] Many products, particularly food products are sensitive to thepresence of oxygen and/or the loss or absorption of water. Theseproducts are susceptible to deterioration, when packaged, due to oxygenand/or moisture absorption or loss through the wall of the package.Attempts to solve the problem have led to the widespread use of oxygenbarriers and/or moisture barriers in packaging materials. Typicalmoisture barriers include polyethylene and polypropylene. Suitableoxygen barriers include EVOH, PVCH, Nylon and blends thereof. Vinylidenechloride—vinyl chloride copolymers and vinylidene chloride—methylacrzlate copolymers are suitable as both moisture and oxygen barriers.

[0004] A problem with conventional barrier materials is that due totheir high cost or their unstable structural characteristics or otherweaknesses, it is difficult to fabricate commercial packaging solely outof barrier materials. For instance, EVOH, while having superior oxygenbarrier properties, suffers moisture problems because of the manyhydroxyl groups in the polymer. Other barrier materials are so expensivethat to manufacture structures solely from those barriers would be costprohibitive. Accordingly, it has become a common practice to usemultilayer structures, whereby, the amount of expensive or sensitivebarrier material may be reduced to a thin layer and an inexpensivepolymer can be used on one or both sides of the barrier layer asstructural layers. In addition, the use of multilayer structures permitsthe barrier layer to be protected from Deterioration by structurallayers on one or both sides of the barrier layer.

[0005] Although multilayer structures containing a barrier layer may becheaper and stronger than a single layer of barrier materials, suchstructures are more complicated to Manufacture than single-layered ones.In addition, multilayer structures comprised of layers of a variety ofdifferent materials may be opposed in some instances on environmentalgrounds, they may be more difficult to recycle since it is oftendifficult and expensive to separate the layers. In addition, reducingthe thickness of the barrier layer in a multilayer structure can reducethe barrier properties of the film. Accordingly, there is a need for asingle-layer packaging material with suitable barrier properties butwithout the cost or structural weaknesses of packaging made solely froma barrier material. There is also a need for additional multilayerstructures having improved barrier properties wherein, the barriermaterial is reduced to a thinner layer and replace in part byinexpensive structural layers. These structures have the same barrierproperties of prior art barriers but at lower cost due to a decrease inthe amount of expensive barrier material used.

[0006] In addition to barrier properties, it is frequently desirable touse materials which have oxygen absorption capabilities. These oxygenabsorption or oxygen scavenging materials are useful in reducing theamount of oxygen that contaminate the product packaged in the container.An example of oxygen scavenging materials and methods of using them isdisclosed in U.S. Pat. No. 4,425,410 to Farrell et al, the disclosure ofwhich is hereby incorporated by reference herein. Another useful aspectof oxygen absorbing material is that such materials can reduce residualoxygen which is trapped in the headspace of a container during sealing,thereby preventing it from having a deleterious effect on the packagedproducts.

[0007] A material that is commonly used in Packaging applications ispolyethylene terephthalate resin, hereinafter referred to as PET. WhilePET has a number of valuable properties in packaging, it does not Staveas good a gas barrier property as is frequently required or desired inmany applications. For example, although PET has good carbon dioxidebarrier properties for soft drinks, it has not been found useful inpackaging such products as beer because beer rapidly loses its flavordue to oxygen migration to the bottle. Similar problems are encounteredwith citrus products, tomato based products and aseptically packed meat.A packaging material with physical properties similar to PET ispolyethylene naphthalate (PEN) which is 3-20 times more effective as abarrier but is considerably more expensive.

[0008] In order to enhance polyester's gas barrier properties,polyesters have been used in a multilayer structure in combination witha layer having excellent gas barrier properties such as EVOH. However,multilayer structures employing polyester, such as PET, Frequently haveadhesion problems between the polyester and the barrier layer whichfrequently leads to delamination over time.

[0009] One approach to enhancing the gas barrier property of PET is touse a resin mixture which includes PET and a xylylene group containingpolyamide resin. Such resin materials are disclosed in U.S. Pat. No.4,501,781 to Kushida en al. One of the considerations encountered withsuch blends accordingly to Kushida is that there is a limit to theamount of xylylene group-containing polyamide resin that may be presentin the PET blend. Kushida indicates that amounts of xylylenegroup-containing polyamide resin greater than 30% by weight causes thecontainer to become a laminated foil structure which is susceptible toexfoliation between the foil layers of the container.

[0010] According to Kushida, the permeation of oxygen gas through thewalls of a container is less when the container is made with PET and axylylene group-containing polyamide than when the container is madesolely of PET. Kushida reports that a bottle shaped container made withPET-xylylene group-containing polyamide measured 0.0001 cc of oxygenPermeation per day compared to 0.0180 cc of oxygen permeation per dayfor a container made with PET.

[0011] A preferred xylylene group-containing polyamide resin in thepresent invention is an aromatic polyamide formed by polymerizingmeta-xylylene-diamine (H₂NCH₂—m—C₆H₄—CH₂NH₂) with adipic acid(HO₂C(CH₂)₄CO₂H) . The most preferred such polymer is manufactured andsold by Mitsubishi Gas Chemicals, Japan, under the designation MXD6 orMXD6 nylon.

[0012] In U.S. application Ser. No. 07/472,400 to Hong et al., the gasbarrier property of polyester is enhanced by blending polyester withxylylene group-containing polyamide and a transition metal catalyst.Preferred embodiments include blends of PET/MXD6/Cobalt and exhibitsuperior oxygen barrier and oxygen absorption characteristics that werenot present in the prior art structures. However, the structures in thisinvent-on are not as clear as the prior art structures. Hong disclosesthat it is believed that the high orientation of the blend increases thesurface areas and interface between PET and MXD6 nylon so that there area greater number of sites at which a reaction or an absorption of oxygencatalyzed by the transition metal catalyst takes place. This increasedsurface area and interface between PET and MXD6 nylon also causes achange in the refractive characteristics of the materials and results inan increased diffusion of light passing through the structures. Thedisclosures made in the Hong application are hereby incorporated byreference herein.

[0013] In U.S. Pat. No. 4,407,873 to Christensen et al., the need forthe proper selection of materials in films used in retort applicationsis discusses. Common to the requirements of retort pouch packaging isthe requirement that the filled and sealed package be subjected tosterilizing conditions of relatively high temperature after the pouch isfilled with product and sealed. Typical sterilizing conditions range inseverity up to about 275° F. with residence times at that temperature ofas much as 30 minutes or more. Such conditions impose severe stresses onthe packages. Many packaging structures provide excellent protection forthe package contents at less severe conditions. Or example, relativelysimple packaging structures for packaging requiring the ability towithstand boiling water, such as at 212° F. are readily available fromseveral suppliers. When sterilizing conditions are required, however,most of these packages fail to survive the processing. Typically,problems are encountered with excessive weakening or failure of the heatseals about the periphery of the couch. Also certain weaknesses orseparations ray develop between the layers in the multiple layer sheetstructure In addition, the high humidity experienced during thesterilizing process can change the chemical or structural properties ofsome materials.

[0014] While Hong reports improved barrier properties usingPET/MXD6/cobalt blends, there is a further need for oxygen barriers ofgreater clarity. In addition, there is a need for compositions which canbe used in retort application in addition to acting as a clear oxygenbarrier material thus, it is an object of the present invention toprovide an improved monolayer barrier structure that satisfies bothclarity and retort functions.

[0015] It is also an object of the present invention to provide a clearmonolayer barrier structure that has barrier properties superior toknown barrier materials.

[0016] It is a further object of the present invention to provide amultilayer structure having a layer comprising an MXD6/cobalt blend thatdoes not delaminate under conditions of high relative humidity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 shows a pouch, sealed on three sides and made with thesheet structure of this invention.

[0018]FIG. 2 shows a cross-section of the pouch of FIG. 1 taken at 2-2of FIG. 1.

[0019]FIG. 3 shows a cross-section of sheet structure used to form thepouch shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

[0020] It has been discovered that the oxygen barrier properties of MXD6nylon are improved by the addition of cobalt octoate and that structuresformed from MXD6/cobalt octoate blends and MXD6/cobalt octoate/PETblends have improved clarity and retort characteristics. The blends canbe made into structures in the form of containers, films, sheets,pouches or lidstock. When used in a film, he MXD6/cobalt salt blend andthe MXD6/cobalt salt/PET blend can be a single layer film or one layerof a multiple layer film which has been coextruded, extrusion coated orlaminated.

[0021] Although PET is the preferred polyester used in the MXD6/cobaltoctoate/polyster blends, any thermoformable grade polyester with oxygenbarrier qualities greater than those of polyolefins can be used.

[0022] The addition of cobalt octoate to MXD6 nylon, or to a blend ofMXD6 nylon and PET, produces blends that are significantly moreimpervious to oxygen than structures of MXD6 nylon or MXD6 nylon/PETblends. The improved barrier properties of the compositions of thepresent invention are unaffected by fluctuations of temperature andhumidity. The oxygen barrier properties of previously known barrierpolymers such as EVOH are adversely affected at 100% relative humidityRH) and so they must be protected by a moisture barrier polymer. In cuepresent invention, it has been discovered that the addition of cobaltoctoate in an amount of up to about 250 ppm to a xylylenegroup-containing polyamide, preferably MXD6, or a xylylene groupcontaining polyamide and polyester (preferably PET) blend produces ablend that does not require protection from 100% RH and thus, eliminatesthe need for a moisture barrier layer.

[0023] Structures containing PET/MXD6/Cobalt oczoate blends orMXD6/cobalt octoate blends known in the art are oriented to increaseoxygen barrier and oxygen absorption. However, such orientation ray havea deleterious effect on the color and clarity of the structure. Theseproblems are caused by a change in the refractive index of the materialswhen the polymers are oriented. Orientation enlarges the domain size ofMXD6 so that it is greater than the wavelength of light and this resultsin the increased scattering of light. See Table 1. In the presentinvention, knowledge of the processing and orientation characteristicsof she MXD6/cobalt octoate blends and MXD6/cobalt octoate. PET blends isutilized to produce clear structures having improved oxygen barrierproperties by limiting the degree of orientation so that the MXD6 domainincreases in size up to less than the wavelength of light. TABLE 1 THEEFFECT OF REFRACTIVE INDEX AND PARTICLE SIZE ON HAZE ORIENTATIONREFRACTIVE INDEX PARTICLE NORMALIZED BLEND DRAWDOWN MXD 6 PET SIZE (um)HAZE (% HAZE/MIL) 0 1.580 1.578 0.1-0.3 0.2 9 1.589 1.620 2-4 0.8

[0024] The oxygen barrier and oxygen absorbing compositions of thepresent invention can also be formed into multiple Layer structures.These multiple layer structures have a core layer of either a MXD6nylon/cobalt octoate blend or a MXD6 nylon/polyester/cobalt octoateblend disposed between two adjacent layers. The two adjacent layers arecomprised of either a Polyester or a polyamide. Also, one adjacent layercan be a polyester and the other adjacent layer can be a polyamide. Inpreferred embodiments, the polyester is PET and the polyamide is nylon6. In another preferred embodiment, these structures are orientated to adegree so that the MXD6 domain increases in size up to less than thewavelength of light.

[0025] In the present invention, any thermoformable grade polyester withoxygen barrier qualities greater than those of polyolefins, can be usedto form clear packages and containers with almost zero oxygenpermeability when blended with MXD6 and cobalt octzate. It has beendiscovered that the problem of haze is solved by extrusion blow moldingthe blend when it is in a molten state. This minimizes the orientationthat occurs when the packages or containers are fabricated. By limitingthe orientation, the domain sizes of the polyester and MXD6 do notincrease to where they are greater than the wavelength of light anddiffusion occurs.

[0026] Table 2 shows a comparison of the amount of haze in bottlesproduced by extrusion blow molding and injection-reheat blow molding.The extrusion blow molded bottles display a significant reduction in thepercent haze. TABLE 2 COMPARISON OF THE HAZE OF INJECTION BLOW MOLDEDAND EXTRUSION BLOW MOLDED BOTTLES NORMALIZED HAZE BOTTLES (% HAZE/MIL)INJECTION-REHEAT 3.16 BLOW MOLDED EXTRUSION BLOW 0.2 MOLDED-MATTE FINISHMOLD EXTRUSION BLOW 0.12 MOLDED-POLISHED MOLD

[0027] Cast film were prepared using Selar polyester which was blendedwith MXD6 nylon with and without the addition of cobalt octoate. In thepresence of MXD6, these films showed a mild grey color. However, whenthese films were thermoformed, clear structures were produced. Moreover,haze was significantly reduced by minimizing the degree of orientation.Table 3 shows the normalized % haze/mil of materials compared to haze ininjection-reheat blow molded bottles. TABLE 3 MEASUREMENTS OF %HAZE/THICKNESS (% HAZE/MIL) Cast Film Formed Into Injection-Blow CastFilm Thermoformed Meat Molded Bottles Material Unoriented PackagesOriented Selar PT207 0.2 0.18 0.16 Selar PT207 + 0.25 0.3 3.16 7.5% MXD6+120 PPM Cobalt

[0028] The composition of the present invention also comprises a blendof polyester, such a PET, and up to about 30% of a barrier material,such as a xylylene group-containing polyamide with about 49 ppm to about110 ppm catalyst, most preferably in the form of a nascent catalystresidue from the PET. The barrier material is preferably a xylylenegroup-containing polyamide rein commonly known as MXD6 nylon which isavailable from Toyobo or Mitsubishi Gas Chemicals Company. The PET isavailable from Eastman Hoechst Celanese, ICI America, Shell Chemical orDuPont. The catalyst is a transition metal. Cobalt has been found to beParticularly useful in the present invention. Transition metal catalystsare defined as catalysts of metals which have filled or partially filledouter “d” orbitals or are those having filled “d” orbitals and filled orpartially filled “p” orbitals.

[0029] Multi-layer structures having a barrier layer of MXD6 nylon andtwo outer layers of PET wherein the MXD6 nylon comprises about 10 wt. %of the total structure will provide a clear film or ccrtainer. However,the oxygen barrier properties of such multilayer structures are not asgood as blends of the present invention. In addition, such multiayerstructures will not provide the oxygen absorption capabilities of thepresent invention.

[0030] In blending the polyester with the oxygen barrier material, it ispreferable that a physical blend of the pellets be made in a suitablemixing device. The process disperses the particles of he barriermaterial in the polyester. In one embodiment of the present invention,PET, MXD6 nylon and cobalt salt are mixed together in a screw extruderto form a blend. This extrusion is then oriented to a limited degree byextrusion blow-molding to form a structure such as a container orbottle. When barrier material is blended with polyester, the barriermaterial is normally present as spherical particles dispersed in PET.

[0031] Containers made in accordance with this method are clear, unlikethe prior art structures described above. However, these containersexhibit the same superior oxygen barrier and oxygen absorptioncharacteristics of the prior art structures disclosed by Hong. In asecond embodiment, a blend consisting of PET, up to about 30 wt. % MXD6nylon (preferably up to 10 wt. % MXD6 nylon) and up to about 110 ppmcobalt salt is coextruded as a barrier Layer with a layer of PET on eachsurface thereof to form a three layer structure. In a preferredembodiment for example, the barrier layer would be a blend of 10 wt. %MXD6 nylon and the overall percentage of MXD6 nylon in the structurewould be about 2 wt. %. Containers made from this structure are clearand do not exhibit the haze found in prior art containers. In addition,the catalyst in the blends of the present invention improves the barrierproperties of structures made therefrom by providing oxygen absorptioncapabilities.

[0032] It has been discovered that compositions of blends of a xylylenegroup—containing polyamide and up to 250 PPM of a transition metalcatalyst do not have heir oxygen barrier characteristics adverselyaffected by the high relative humidity conditions experienced duringretort. Therefore, they can be used to form films that do not requireadditional moisture barrier layers. The preferred blends of thesecompositions are comprised of MXD6 and cobalt octoate and they are usedto form the oxygen barrier layer of a single or multiple layer film.When used in a multiple layer film, the barrier layer is disposedbetween two adjacent layers. One, or both, of the adjacent layers iscomprised of a polyester or a polyamide. The preferred polyester As PETand the preferred polyamide is nylon 6. In one embodiment of the presentinvention, these compositions are oriented to a degree so that the MXD6domain increases in size up to less than the wavelength of light.

[0033] The invention will now be described in detail and in relation tothe drawings. FIG. 1 illustrates a pouch such as is the desiredpackaging structure of one of the embodiments of this invention. Across-section of a portion of the pouch is shown in FIG. 2. The sheetmaterial used to make the pouch is seen in FIG. 3. By comparison ofFIGS. 2 and 3 it is seen that the FIG. 2 construction consists of twosheet elements of the FIG. 3 construction in face to face relation withthe layers 12 joined at the one edge in heat seal. The pouch is formedby arranging the two sheet elements in face to face relationship andforming heat seals 19 about the common periphery. Alternately, the pouchmay be formed by folding a sheet element onto itself and forming heatseals about the edges. Either way the formed pouch appears as shown inFIG. 1.

[0034] Referring now to FIGS. 2 and is, layer 12 is a heat sealablelayer comprised of a polyester or a polyamide. Layer 14 is an optionaladhesive, or tie layer, selected based on the materials in the adjacentlayers. Layer 16 a blend of a xylylene group-containing polyamide and upto 250 ppm of a transition metal catalyst. Layer 18 is also an optionaladhesive, or tie, layer and is also selected based on the materials inthe adjacent layers. Layer 20 is an outer protective layer comprised ofa polyester or a polyamide.

[0035] The formed pouch is intended for packaging products which aresubjected to a sterilizing process after the product is in the packageand the package is sealed. A common sterilizing process is known asautoclave, or retort, processing. In this process, closed and sealedpackages are placed in a pressure vessel. Steam and water are thenintroduced into the vessel at about 275° F. at a sufficiently highpressure to permit maintenance of the desired temperature. Thetemperature and pressure are usually maintained for about 30 minutes.Finally, the pressure vessel is cooled and the pressure temporarilymaintained until the packages cool Internally. Finally the pressure isreleased and the processed packages are removed.

[0036] Sheet structures of this invention generally range in thicknessfrom about 3 mils up to about 10 mils. The thickest layer is usually thesealant layer and the thinnest layers usually are the tie layers and theoxygen barrier layer.

[0037] The sheet structures of this invention may be made byconventional processes and combinations of processes. The process andits sequences may be selected according to the equipment and polymersavailable. The specific structure selected and the compositions of theoxygen barrier layer and the outer layers of polyester will be at leastpartially dependent on the process and its sequences.

[0038] Both the orientation and the large amounts of catalysts used inprior art structures frequently had a deleterious effect on haze, colorand other properties of the structure. These undesirable effects havebeen overcome in the present invention by controlling the degree oforientation and limiting the amount of catalyst to levels that do notchange the refractive characteristics and color, respectively of theblend materials.

[0039] Prior art structures that used cobalt as a catalyst tended toappear green in color. In the present invention, his problem has beensolved by controlling the amount of cobalt added to the barrier blendmaterial. The result is an improved structure that is clear and freefrom the green tint of the prior art structures.

[0040] Although the detailed absorption/reaction mechanism Is not fullyunderstood, concentrations of about 49 ppm to about 120 ppm residualcatalyst in a polyester-barrier material blend, such as a PET-xylylenegroup-containing polyamide resin blend, have not only superior oxygenbarrier properties but also significant oxygen scavenging capabilities.

[0041] Thus, in the present invention there is provided a compositionhaving superior oxygen barrier and oxygen absorption characteristics.This composition may be employed as a mono or multilayer film, such as,for example, in a pouch or flexible lidstock. These compositions mayalso be formed into rigid containers or may comprise the sidewall, body,lid or entire container. Also, the composition of the present inventionmay be formed into a chip and used in a container as an oxygenscavenger.

[0042] A preferred embodiment of the present invention is a bend of PETand MXD6 nylon, wherein the MXD6 nylon is present in an amount of fromabout 2.5 weight % to about 15 weight % with the balance being PET.Cobalt is present in a range of 49 ppm to about 120 ppm with 62 ppmbeing most preferable. Another embodiment is pure MXD6 with between 49and 120 ppm cobalt.

[0043] In a more preferred embodiment, the MXD6 nylon is present in anamount of from about 4 weight % to about 10 weight % with the balancebeing PET. Cobalt is preferably present in the range of from about 49ppm to about 120 ppm and most preferably present in an amount of about62 ppm.

[0044] In the most preferred embodiment, MXD6 nylon is present In theblend in an amount of about 7.5% with the remainder being PET andcobalt, present in the amounts stated above.

[0045] In some PET, nascent cobalt is present as a residual of the PETpolymerization catalyst. Specially added cobalt is preferably present asa cobalt salt dispersed in mineral spirits such as that sold under thetrademark Nuodex by Huls America. The Nuodex products contain up toabout 15% by weight cobalt. The preferred maximum amount of catalyst isabout 250 ppm and is dependent on the structure being formed from thePET/MXD6/cobalt blends.

[0046] The xylylene group containing polyamide is preferably a MXD6nylon which is produced by condensation polymerization of metha-xylylenediamine (MXDA) and adipic acid.

[0047] In biaxially orienting the blends of the present invention, it ispreferred that the degree of orientation not exceed the limit at whichthe refractive characteristics of the blend materials change and theclarity of the structures deteriorates.

[0048] In one of the embodiments of the invention, the multiple layersheet structures have outer layers comprised of polyesters or polyamidesthat are suitable for heat sealing.

[0049] In another embodiment, an adhesive layer is disposed on one orboth sides of the barrier blend layer to bond the polyester or polyamidelayers to the blend layer.

[0050] One of the embodiments of the present invention relates to theimprovement in the clarity of polyester/xylylene group containingpolyamide blend bottles through a change in the process rather than achange in the materials used. The preferred blends are comprised of PETand MXD6 nylon. It is known in the art that the color in PET/MXD6structures is due to the presence of catalyst residue in the polyester.This color can be controlled by limiting the amount of catalyst. Also,the orientation of PET and MXD6 during the manufacturing process (twostage injection—reheat blow molding) results in the development of hazecaused by refractive index chances and the enlarged domains of MXD6.

[0051] The present invention provides a solution to the problems ofcolor and haze by using the extrusion blow-molding process andextrudable Polyester. The preferred polyester is PET. In extrusion blowmolding, the bottle is produced when the polymer is in its molten stateand therefore, the orientation is minimized. It is believed that hedomain size of unoriented MXD6 is less than the wavelength of light andthe refractive indices of PET and MXD6 are nearly the same. Thus, lightpassing through unoriented MXD6 structures does not scatter and producehaze.

[0052] When multilayer, coextruded bottles are produced thepolyester/MXD6/cobalt blend is disposed between two polyester layers.The preferred polyester is PET.

[0053] The cobalt octoate is present in an amount of up to 250 ppm. Thepreferred amount is 120 ppm.

[0054] Clear, non-hazy structures with PET/MXD6/cobalt blends have beensuccessfully prepared using the extrusion blow-molding process.Multilayer, coextruded bottles having a core layer of 92.5% PET/7.5%.MXD6/120 ppm cobalt were successfully prepared using the process.

EXAMPLE 1

[0055] As an example of this invention, cast films consisting of MXD6nylon and 250 ppm cobalt octcate were prepared in thicknesses from 5 to35 mils and were tested for oxygen permeations against cast films ofMXD6 nylon without cobalt octoate. The results shown below in Table 4demonstrate the improved oxygen barrier characteristics of films of MXD6nylon and cobalt octoate. TABLE 4 oxygen permeation (ccmil/m*2 day)(green cast films at 0% RH) thickness (hrs) Variables (mils) 36 84 180276 324 I. MXD6 film  5 17 15  5 11 12  9 15 13  9 — — 19 30 12 12 — —32 93 38 13  7 12 II. MXD6  5  8  3  1 0.3 0.5 film + 250 ppm 11 —  0  2— — Co 19 23  1  2 — — 35 39  0  2 — —

EXAMPLE 2

[0056] A three layer structure of the present invention having outerlayers of PET and a core layer of MXD6 nylon/100 ppm cobalt octoateblend (wherein the core layer comprised 10% of the structure) was usedto produce bottles on a Nissei stretch blow molding machine. Otherbottles were produced by the same means and from similar material exceptthe core layer did not contain cobalt. After the bottles were aged forthree months at 0% relative humidity, they were tested for oxygenpermeation. The results are shown below in table 5. TABLE 5 thicknessoxygen permeation Variables (mils) (ccmil/m*2 day) (1) PET/MXD6/PET 2742 (2) PET/MXD6 + 100 ppm Co/PET 28  9

EXAMPLE 3

[0057] Flexible lidstock or pouches can be formed from coextruded filmstructures in accordance with the present invention having a core layerof a blend of MXD6 nylon and cobalt octoate disposed between two layersof nylon 6. The film was tested before and after retort for oxygenpermeation at test conditions of 100% oxygen, 0% relative humidity (RH)and at 100% oxygen, 100% RH. The results are shown below in tables 6 and7. TABLE 6 (TEST CONDITIONS: 100% OXYGEN; 0% RH; UNAGED SAMPLE) TOTALSTEADY STATE THICKNESS PERMEATION SAMPLE (MILS) RATE* POST RETORT NYLON6/1 MIL 3.53 6.2 MXD6+120 PPM Co/NYLON 6 PRE RETORT NYLON 6/2 MIL 4.440.1 MXD6+120 PPM Co/NYLON 6 POST RETORT NYLON 6/2 MIL 4.74 0.1 MXD6+120PPM Co/NYLON 6 PRE RETORT NYLON 6/1 MIL 3.31 0.6 MXD6+250 PPM Co/NYLON 6POST RETORT NYLON 6/1 MIL 3.38 3.2 MXD6+250 PPM Co/NYLON 6 PRE RETORTNYLON 6/2 MIL 4.50 0.2 MXD6+250 PPM Co/NYLON 6 POST RETORT NYLON 6/2 MIL4.84 0.0 MXD6+250 PPM Co/NYLON 6 PRE RETORT NYLON 6 3.14 48.0 POSTRETORT NYLON 6 2.88 39.4

[0058] TABLE 7 (TEST CONDITIONS: 100% OXYGEN; 100% RH; UNAGED SAMPLE)TOTAL STEADY STATE THICKNESS PERMEATION SAMPLE (MILS) RATE* POST RETORTNYLON 6/1 MIL 3.53 60.4 MXD6+120 PPM Co/NYLON 6 PRE RETORT NYLON 6/2 MIL4.44 31.4 MXD6+120 PPM Co/NYLON 6 POST RETORT NYLON 6/2 MIL 4.74 2.6MXD6+120 PPM Co NYLON 6 PRE RETORT NYLON 6/1 MIL 3.31 6.6 MXD6+250 PPMCo/NYLON 6 POST RETORT NYLON 6/1 MIL 3.38 22.4 MXD6+250 PPM Co/NYLON 6PRE RETORT NYLON 6/2 MIL 4.50 2.6 MXD6+250 PPM Co/NYLON 6 POST RETORTNYLON 6/2 MIL 4.84 0.2 MXD6+250 PPM Co/NYLON 6 PRE RETORT NYLON 6 3.14288 POST RETORT NYLON 6 2.88 314

What we claim is:
 1. An improved clear oxygen barrier and oxygenabsorbing multiple layer structure comprising a core layer comprising ablend of a xylylene group-containing polyamide and up to 250 ppm of atransition metal catalyst disposed between two polyester layers.
 2. Afilm made from the multiple layer structure of claim
 1. 3. A containermade from the multiple layer structure of claim
 1. 4. A multiple layerstructure according to claim 1, wherein, the xylylene group-containingpolyamide is MXD6 nylon and the transition metal is cobalt octoate.
 5. Afilm made from the multiple layer structure of claim
 4. 6. A containermade from the multiple layer structure of claim
 4. 7. An improved clearoxygen carrier and oxygen absorbing multiple layer structure comprisinga core layer comprising a blend of MXD6 nylon and up to about 250 ppmcobalt octoate disposed between two layers of PET.
 8. A film made fromthe multiple layer structure of claim
 7. 9. A container made from themultiple layer structure of claim
 7. 10. An improved clear oxygenbarrier and oxygen absorbing composition comprising a blend ofpolyester, a xylylene group-containing polyamide and up to 250 ppm of atransition metal catalyst, wherein, the composition is oriented to adegree so that the MXD6 domain increases in size up to less than thewavelength of light.
 11. A composition according to claim 10, whereinthe polyester is PET and the catalyst is cobalt.
 12. A compositionaccording to claim 10, wherein, the polyamide is MXD6 and the catalystis cobalt.
 13. A composition according to claim 10, wherein, thepolyester is PET, the polyamide is MXD6 and the catalyst is up to 120ppm cobalt octoate.
 14. A film made from the composition of claim 10.15. A container made from the composition of claim
 10. 16. A film madefrom the composition of claim
 11. 17. A container made from thecomposition of claim
 11. 18. A film made from the composition of claim12.
 19. A container made from the composition of claim
 12. 20. A filmmade from the composition of claim
 13. 21. A container made from thecomposition of claim
 13. 22. An improved clear oxygen barrier and oxygenabsorbing composition comprising a blend of a polyester with oxygenbarrier properties greater than polyolefins, a xylylene group-containingpolyamide and up to 250 ppm of a transition metal catalyst.
 23. Thecomposition of claim 22, wherein the polyester is PET, the polyamide isMXD6 nylon and the transition metal is cobalt octoate.
 24. A film madefrom the composition of claim 22, wherein, the film is oriented so thatthe MXD6 domain increases in size up to less than the wavelength oflight.
 25. A container made from the composition of claim
 22. 26. A filmmade from the composition of claim
 23. 27. A container made from thecomposition of claim
 23. 28. An improved clear oxygen barrier and oxygenabsorbing multiple layer structure comprising a blend of a firstpolyester, a xylylene group-containing polyamide and up to 250 ppm of atransition metal catalyst disposed between two layers of a secondpolyester, wherein, the structure is oriented to a degree so that theMXD6 domain increases in size up to less than the wavelength of light.29. A multiple layer structure according to claim 28, wherein, the firstpolyester is PET, the polyamide is MXD6 nylon and the catalyst is up to120 ppm cobalt octoate.
 30. A multiple layer structure according toclaim 28, wherein, the first and second polyesters are PET, thepoylamide is MXD6 and the catalyst is cobalt octoate.
 31. A film madefrom the multiple layer structure of claim
 28. 32. A film made from themultiple layer structure of claim
 29. 33. A film made from the multiplelayer structure of claim
 30. 34. An improved clear oxygen barrier andoxygen absorbing multiple layer flexible packaging structure, wherein,the layers are firmly adhered to each other in face to face contact, thestructure comprising, in order: (a) a heat sealant layer comprising apolyamide, (b) an oxygen barrier and oxygen absorbing core layercomprising a blend of a xylylene group-containing polyamide and up to250 ppm of a transition metal catalyst. (c) an outer protective layercomprised of a polyamide.
 35. The packaging structure of claim 34,wherein, the structure is oriented so that the MXD6 domain increases insize up to less than the wavelength of light.
 36. A multiple layerflexible packaging structure according to claim 34, wherein, adhesivelayers are disposed on either side of and adjacent to the oxygen barriercore layer.
 37. A multiple layer flexible packaging structure accordingto claim 34, wherein, :he heat sealant layer and the outer protectivelayer are comprised of nylon
 6. 38. A multiple layer flexible packagingstructure according to claim 34, wherein, the core layer is comprised ofa blend of MXD6 nylon and cobalt octoate.
 39. A multiple layer flexiblepackaging structure according to claim 34, wherein, the heat sealantlayer and the outer protective layer are comprise of nylon 6 and theoxygen barrier core layer of a blend of MXD6 and cobalt octoate.
 40. Aretortable food pouch fabricated from the multiple layer flexiblepackaging structures of claim
 34. 41. A retortable food pouch fabricatedfrom the multiple layer flexible packaging structures of claim
 36. 42. Aretortable food pouch fabricated from the multiple layer flexiblepackaging structures of claim
 37. 43. A retortable food pouch fabricatedfrom the multiple layer flexible packaging structures of claim
 38. 44. Aretortable food pouch fabricated from the multiple layer flexiblepackaging structures of claim
 39. 45. An improved clear oxygen barrierand oxygen absorbing multiple layer flexible packaging structure,wherein, the layers are firmly adhered to each other in face to facecontact, the structure comprising, in order: (a) a heat sealant layer ofnylon 6; (b) an oxygen barrier and oxygen absorbing core layercomprising a blend of MXD6 and 120 ppm cobalt octoate; and (c) an outerprotective layer of nylon 6; wherein, the packaging structure issuitable for retort applications.
 46. A retortable food pouch fabricatedfrom the multiple layer flexible packaging structure of claim
 45. 47. Amethod of making an improved clear oxygen barrier and oxygen absorbingcontainer comprising the steps of: (a) blending a polyester, a xylylenegroup-containing polyamide and up to about 250 ppm of a transition metalcatalyst; (b) heating the blend into a molten state; and (c) extrusionblow molding a container from the molten blend.
 48. A method accordingto claim 47 wherein, the polyamide in the blend is MXD6 and the catalystis cobalt octoate.
 49. A method according to claim 47, wherein, thepolyester is PET.
 50. A method according to claim 47, wherein, thepolyester is PET, the polyamide is MXD6 and the catalyst is cobaltoctoate.
 51. A method according to claim 50, wherein, the MXD6 ispresent inn an amount of from about 2.5 wt. % to about 15 wt. % of theblend.
 52. A method according to claim 50, wherein, the MXD6 is presentin an amount of from about 2.5 wt. % to about 15 wt. % of the blend andthe cobalt octoate is present in an amount of from about 49 ppm to about120 ppm.
 53. A method according to claim 50, wherein, the MXD6 ispresent in an amount of from about 4 wt. % to about 10 wt. % of theblend.
 54. A method according to claim 50, wherein, the MXD6 is presentin an amount of from about 4 wt. % to about 10 wt. % of the blend andthe cobalt octoate is present in an amount of from about 49 ppm to about120 ppm.
 55. A method according to claim 50, wherein, the MXD6 ispresent in an amount of from about 4 wt. % to about 10 wt. % of theblend and the cobalt octoate is present in an amount of about 62 ppm.56. A method according to claim 50, wherein, the MXD6 is present in anamount of about 7.5 wt. % of the blend and the cobalt is present in theamount of about 62 ppm.
 57. A container made by the method of claim 52.58. A container made by the method of claim
 54. 59. A container made bythe method of claim
 55. 60. A container made by the method of claim 56.61. A method for making an improved clear oxygen barrier and oxygenabsorbing multiple layer container comprising the steps of: (a) blendinga first polyester, a xylylene group-containing polyamide and up to about250 ppm of a transition metal catalyst; (b) heating the blend into amolten state; (c) heating a second polyester into a molten state; and(d) coextrusion blow-molding a container from the molten blend and thesecond polyester; wherein, the coextrusion comprises a blend layerdisposed between two layers of polyester.
 62. A method according toclaim 6, wherein, the polyamide in the blend is MXD6, the polyester inthe blend is PET and the catalyst is cobalt octoate.
 63. A methodaccording to claim 62, wherein the second polyester is PET.
 64. A methodaccording to claim 61, wherein, the MXD6 is present in an amount of fromabout 4 wt. % to about 10 wt. % of the blend and the cobalt octoate ispresent in an amount of from about 49 ppm to about 120 ppm and thesecond polyester is PET.
 65. A method according to claim 61, wherein,the MXD6 is present in an amount of about 7.5 wt. % of the blend, thecobalt octoate is present in an amount of about 100 ppm and the secondpolyester is PET.
 66. A container made by the method of claim
 61. 67. Acontainer made by the method of claim
 62. 68. A container made by themethod of claim
 63. 69. A container made by the method of claim
 64. 70.A container made by the method of claim 65.